1. Field of the Invention
The present invention relates generally to electronic packaging of semiconductor integrated circuits. More specifically, the present invention relates to electronic packaging of photo-sensing semiconductor devices having a sealing structure for protecting a photo-sensing area of one or more photo-sensing devices.
2. Related Art
Novel electronic packaging techniques for applications incorporating photo-sensors are disclosed in co-pending U.S. patent application Ser. Nos. 10/692,816, 60/507,100, 10/829,273, and 60/536,536, the disclosures of which are incorporated herein by reference. FIGS. 1-2B illustratively show schematic cross-sectional views of certain exemplary electronic packages realized by such techniques, fuller descriptions of which are contained in such co-pending applications.
The package illustrated in FIG. 1 is typically suited for general applications, while that shown in FIGS. 2A, B is particularly well-suited for cellular telephone camera module applications, where compact size remains invariably among paramount concerns.
In packages of the type shown, a photo sensor device defines a certain photo-sensing area—defined at a center portion of a top surface in the configurations illustrated. A substrate having sufficient transmittance to light within a certain wavelength range of interest is provided with the photo sensor device. The substrate may be formed, for example, of a glass material where the photo-sensor device is to sense light, within the visual range in wavelength. Electrical interconnection lines and one or more passivation layers are formed over a front surface of the substrate (bottom surface of the substrate in the configuration illustrated); and, flipchip interconnections are typically employed between the photo-sensor device and substrate. A sealing structure is also provided for protecting the side wall portion of the photo-sensor device and the photo-sensing area that it extends about. Other structures such as solder balls and decoupling capacitances are also typically provided in the resulting package using suitable means known in the art, but their detailed description is not necessary for a clear understanding of the present invention, and for that reason not included.
A highly effective yet cost-effectively realizable sealing structure is necessary for longevity and reliability in the resulting electronic package. Ideally, the sealing structure would serve to protect the given photo-sensor device from moisture uptake and prevent particulates from entering and contaminating the photo-sensing area. The structure would be configured to define a substantially sealed internal cavity about the photo-sensing area without so encroaching upon the photo-sensing area to diminish the light intensity thereat. Especially where a micro-lens structure is employed atop the photo-sensor device, the substantially sealed structure's formation of such cavity is essential for the micro-lens structure to properly intensify the light onto each photo diode underneath.